Formation of a patch of altocumulus stratiformis perlucidus undulatus clouds as the weather sounding on the third thumbnail indicated a cold front at the 2km level probably trigerring this cloud formation through instability. There was lots of wind shear causing parts of the altocumulus to transform into undulatus though the full undulatus status was never acquired. An upper-level trough was extending from the NW towards the Maltese Islands creating thermal contrast over the Mediterranean. The first thumbnail is a panoramic view of the photographed cloud whilst the second thumbnail is a photo of high clouds being cirrus spissatus and altocumulus castellanus taken in the early afternoon.